How to tile a texture over a cube in cycles?
Basically it's a UV problem:



If faces A and B can be contiguous, at least one between B and E or A and E (my case) will not be seamless, unless you want this effect which is really fake:



Anyway, for the first option, in edit mode select those edges: AE, ED, EC, DC, AF, FD, FC; Mark as seams, U to Unwrap.

For the second option place your viewport as you want to see the cube, select all vertices and press U "project from view".

I noticed also that in your node system the coordinates mapping affects only one of the 3 textures, which generally is an error.